Process of hardening, esterifying, and rehardening artificial protein threads



Patented Oct. 12, 1954 PROCESS- OF HARDENING,

ESTERIFYING,

AND REHARDENING ARTIFICIAL PRO- TEIN THREADS Robert L. Wormell, Coventry,

to Courtaulds Limited, London,

British company England, assignor England, a

N Drawing. Application April 12, 1951, Serial No. 220,727

Claims priority, application Great Britain May 3, 1950 11 Claims. 1

This invention relates to the production of artificial filaments, threads, fibres, bands and the like, hereinafter referred to generally as threads, from casein of animal or vegetable origin, for example lactic or milk casein, peanut protein, soya bean protein, castor bean protein and similar fibre-forming proteins.

It is known to produce such threads by extruding a solution of the protein into a setting medium, for example by extruding a solution of the protein in caustic soda into a coagulating bath containing sodium sulphate and sulphuric acid. It is the usual practice to subject the freshlyextruded threads to the action of formaldehyde, either alone or in conjunction with an acid or one or more salts, in order to harden the threads, that is to make them resistant to cold Water. The threads are then usually further treated in order to render them resistant to hot water and hot aqueous solutions, such a process being known as insolubilising.

The wet properties of artificial protein threads as produced hitherto have not, in general, been entirely satisfactory for some textile purposes. Thus, the threads usually swell appreciably in water and in dilute alkali solutions such as are used in securing and milling, so that fabrics made from protein threads, alone or in admixture with wool, tend to be adversely affected by standard scouring and milling processes. In addition, artificial protein threads which have been dyed have poor fastness to washing, and standard scouring treatments of dyed protein threads usually reduce the depth of shade considerably.

German patent specification No. 748,450 describes a process of dyeing and printing natural or artificial protein fibres or mixtures of such fibres, wherein the fibres, either during or after the dyeing, are treated with methanol in the presence of an esterification catalyst.

The object of the present invention is to improve the wet properties of protein threads.

According to the present invention protein threads having improved wet properties are produced by hardening freshly extruded protein threads in a bath containing formaldehyde and one or more metal salts until the threads are resistant to cold water, treating the hardened threads in a bath comprising methyl alcohol or ethyl alcohol together with an esterification catalyst such as sulphuric acid to eiiect esterification of the threads and then subjecting the esterified threads to a curing treatment, that is to say, either a hardening treatment in a bath CQnr. taining formaldehyde and one or more metal salts or an insolubilising treatment.

The esterification of the hardened threads is preferably effected at a raised temperature, for example at 35 to 50 centigrade.

The preferred esterification catalyst is sulphuric acid but other catalysts such as methyl sulphuric acid and ethyl sulphuric acid may be use.

Preferred hardening baths for use in the pres ent invention are those containing formaldehyde and sodium sulphate although other salts such as magnesium sulphate or aluminium sulphate may also be present in addition to or instead of the sodium sulphate. The hardening bath may also contain an acid such as sulphuric acid. Examples of insolubilising agents for treating the esterified threads are acetic anhydride as described in Brit ish patent specification No. 495,385 and compounds giving rise to cyanate ions as described in British patent specification No. 614,506. The aluminium sulphate baths described in the specification of British application No. 1810'2/50, which effect hardening and insolubilising simultaneously, may also be used. The treatment of the esterified threads with cyanates can conveniently be effected by applying to the thread an aqueous composition containing a soft-finishing compound together with a cyanate and, after removing surplus liquor, baking the thread for a short time, for example at to 10 centigrade.

The prehardened fibres either alone or in admixture With other fibres may be knitted, woven or otherwise formed into a fabric and the fabric may then be treated in an esterification bath followed by a second hardening or insolubilising bath in accordance with the invention.

The esterification liquid containing sulphuric acid and methyl alcohol or ethyl alcohol may also contain Water preferably in a proportion not exceeding 30 per cent by weight based on the weight of the alcohol. Proportions of water of the order of 20 to 25 per cent are particularly suitable. The use of esterification media containing water is usually more economic as compared with the use of similar media which are substantially free from water. Baths containing '75 to per cent of methyl alcohol or ethyl alcohol and 25 to 20 per cent of water, with to 240 grams per litre of sulphuric acid may be used with good results. Such esterification is preferably effected at raised temperatures, temperatures of from 35 to 50 centigrade being particularly suitable. Treatment times are not critical and may conveniently vary from /2 hour to 3 hours, depending on the temperature used and the concentration of the esterification bath.

The addition of a dialkyl sulphate, for example in a proportion of about 30 per cent by weight based on the weight of the alcohol, assists in the esterification. The preferred dialkyl sulphate is diethyl sulphate.

It is also advantageous to pretreat the hardened protein threads immediately before the esterification step with the alcohol used in the esterification or, when a mixture of water and alcohol is used in the esterification bath, with an alcoholwater mixture having the same composition as that present in the esterification bath. This pretreatment step helps to maintain the composition of the esterification bath substantially constant particularly during prolonged operations.

The process according to the invention produces protein threads which are generally white in colour and have reduced water imbibition. Imbibition is defined in Cameron and Morton, Permanent Finishes on Viscose Rayon, Journal of the Society of Dyers and Colorists, October 1948, page 331, and in Proceedings, Journal of the Textile Institute 40, page P678 (1949), as the percent by weight of water retained on the oven dried fiber after centrifuging a 0.5 gram sample for minutes at 1000 g. The fastness to washing of threads dyed with a dispersed dye such as Azo-Geranine (Colour Index No. 31) and with crome dyes is also improved. The threads are also stable to normal hot acid dyebaths containing acid dyes, chrome-complex acid dyes, chrome dyes, and also to normal dyebaths containing direct dyes and solubilised sulphur dyes.

The process according to the invention may include a cutting operation at any convenient stage; the staple fibres produced are particularly suitable for blending with wool in the manufacture of milled articles such as blankets, since the protein fibres are not adversely affected to any appreciable extent by the milling process.

The invention is illustrated by the following examples in which parts and percentages are by weight:

Example 1 A percent solution of milk casein in 1 percent aqueous caustic soda solution was extruded into a coagulant bath. The resultant threads after hardening in formaldehyde were stretched 400 percent and were then hardened further by immersion for 2 hours in a bath at 50 centigrade containing, in each litre of solution, 10 grams of formaldehyde and 400 grams of sodium sulphate; the pH value of the bath was 3.5. The threads were then pressed free from surplus liquor, washed in water, again pressed and then immersed for 4 hours in a bath at 45 centigrade consisting of a mixture of 7 parts of concentrated sulphuric acid (specific gravity 1.84) and 33 parts of ethyl alcohol. The esterified fibres were then washed in water and hardened again for 2 hours in a bath at 45 centigrade containing, in each litre, 10 grams of formaldehyde and 400 grams of sodium sulphate. The fibres were finally washed in water and dried.

The imbibition of the threads obtained in a 1 percent aqueous sodium carbonate solution was 44 percent as compared with 125 percent for corresponding threads which had been hardened only.

Samples of the threads obtained and of comparable threads which had been hardened only were dyed with Azo-Geranine and were then treated in a 0.25 percent soap solution at 45 centigrade. The threads obtained in the example were fast to this washing treatment whereas the 4 threads hardened only were considerably lighter in shade after the same washing treatment. The dyed threads obtained according to the example also withstood 30 minutes heating at 98 centigrade in a bath of N sulphuric acid, whereas the dyed threads hardened only were considerably weakened.

Example 2 A 20 percent solution of milk casein in 1 percent aqueous caustic soda solution was extruded into a coagulant bath. The resultant threads after hardening in formaldehyde were stretched 400 percent and were then hardened further by immersion for 2 hours in a bath at 50 centigrade containing in each litre of solution, 10 grams of formaldehyde and 400 grams of sodium sulphate; the pH value of the bath was 3.5. The threads were then pressed free from surplus liquor, washed in water and then cut to 2 inch staple lengths. The cut staple was dried in a current of warn air. blended with 3 times its weight of wool noils and the blend was spun using the woollen system into yarn of 12 counts. The yarn was then woven into a cloth suitable, after milling, for coatings.

A sample of the fabric was then soaked for 8 hours at 35 centigrade in 20 times its weight of a mixture of 1 part of sulphuric acid and 4 parts of methylated spirit. The fabric was then washed in water till free from acid, and hardened for 2 hours in a bath at 45 centigrade containing, in each litre, 10 grams of formaldehyde and 400 grams of sodium sulphate. The fabric was washed in water, dried and then subjected to a milling operation in a Williams Peace milling machine, using 2Tw. sodium carbonate solution containing percent of soap, at 50 centigrade. Under these conditions the fabric was found to be dimensionally stable, both as regards expansion on wetting and the development of undue shrinkage during milling; the fabric resisted the mechanical action of the milling machine and no holes or other faults developed during the operation.

Example 3 A 20 percent solution of peanut protein in 1 percent aqueous caustic soda solution was extruded into a coagulant bath. The resultant threads after hardening in formaldehyde were stretched 500 percent and were then hardened further by immersion for 2 hours in a bath at 35 centigrade containing, in each litre of solution, 10 grams of formaldehyde, 300 grams of sodium sulphate and 360 grams of sulphuric acid. The threads were then pressed free from surplus liquor, washed in water, again pressed and then immersed for 2 hours in a bath at 45 centigrade consisting of a mixture of- 1 part of sulphuric acid and 4 parts of methylated spirit (74 o. p.). The esterified fibres were then washed in water and hardened for 2 hours in a bath, at 40 centigrade, containing in each litre, 10 grams of formaldehyde and 400 grams of sodium sulphate. The fibres were then washed and dried.

The imbibition of the threads obtained in a 1 percent aqueous sodium carbonate solution was 40 per cent as compared with 81 per cent for corresponding fibres which had been hardened and insolubilised only.

Example 4 A sample of casein thread hardened as described in Example 1 was immersed for 1 hour in a bath at 50 centigrade consisting of a mixture of 4 parts of ethyl alcohol and 1 part of water and containing grams of sulphuric acid per Example 5 The procedure described in Example 4 was repeated using methyl alcohol in place of ethyl alcohol. The imbibition in a 1 percent aqueous sodium carbonate solution of the thread obtained was 58.4 percent.

Example 6 Casein threads hardened as described in Example 1 were soaked in methyl alcohol at 35 centigrade. Surplus alcohol was squeezed out and the fibres were then esterified for one hour at a temperature of 35 centigrate with parts by weight of a liquor consisting of 6.2 parts by volume of methyl alcohol, 2.5 parts by volume of diethyl sulphate and 1 part by volume of sulphuric acid. The esterified fibres were washed until they reacted neutral to methyl red, hydro-extracted and rehardened, washed and dried as described in Example 1.

The imbibition of the product Was 55 percent.

Example 7 Casein fibres extruded and stretched as described in Example 1 were hardened for 2 hours at a temperature of 50 centigrade in a liquor containing, in each litre, 250 grams of aluminium sulphate, 250 grams of sodium sulphate and 10 grams of formaldehyde. The fibres after removal of same composition as described in Example 6 for one hour at centigrade. The esterified fibres were washed and rehardened for 2 hours at centigrade using the same liquor as for the initial hardening. The fibres were finally washed and dried.

The imbibition of the product was 45 percent.

Example 8 fhe moist fibres obtained as described in Example 7 up to the re-hardening stage were imusing as a control a thread prepared as described in Example 8 but excluding only the esterification step. In each case the thread prepared as described in the example was substantially unaffected by the dyeing treatment whereas the dyed control threads were hard and rather brittle.

Samples of the thread of Example 8 were also compared in the same way with dyebaths c'ontaming- Direct dyes:

0.3 percent Chrysophenine G 305 (C. 1.365). 0.5 percent Durazol Blue 2GN'200 (J. S. D. C.,

1943, page 124). 0.65 percent Chlorazol Dark Green PL (C. I. 583). Solubilized sulphur dye:

3 percent Thionol Navy Blue EMS The dyed threads prepared according to Exam- 8 were appreciably superior to the dyed control threads.

Example 9 Casein fibres which had been initially hardened as described in Example 7 were soaked in methyl alcohol at a temperature of 40 centigrade and the excess alcohol removed by squeezing. The fibres were esterified with a liquor consisting of methyl alcohol containing in each litre grams of sulphuric acid. The esterified fibres were washed free from acid and hydro-extracted. The moist fibres were impregnated with a 2 percent solution of sodium cyanate containing 0.1 percent of a soft finish and the excess liquor squeezed out. The fibres Were heated at 70 centigrade for 10 minutes, washed in water and finally dried.

The imbibition oi the product was 70 percent.

The dyeing properties of the product were similar to those of the product of Example 8.

Example 10 fhneads, extruded, hardened and stretched as described in Example 1, were hardened further for 3 hours in a bath at 45 centigrade containing in each litre 550 grams of aluminium sulphate and 20 grams of formaldehyde. The threads were washed free from excess liquor and were then esterified by immersion for 45 minutes in methyl alcohol containing 350 grams per litre of sulphuric acid, this liquor being at a temperature of 35 centigrade. The threads were Washed until they were free from acid and then immersed for 20 minutes in a 4 percent aqueous sodium cyanate solution. Excess solution was removed from the threads by squeezing and the threads were dried at 65 centigrade.

What I claim is:

1. In a process for the production of artificial threads from proteins by extruding a solution of a protein selected from the class consisting of mill: casein, peanut protein, soya bean protein and castor bean protein, into a setting medium, hardening by immersing and freshly-extruded thread so obtained in a bath containing formaldehyde and a metal salt chosen from the group consistin of sodium sulphate, magnesium sulphate, aluminum sulphate and mixtures of said salts until the thread is resistant to the solvent action of cold water and stretching the thread during the said hardening treatment, improving the wet properties of the thread by applying after the hardening step the steps of esterifying the thread in a bath comprising an alcohol chosen from the group consisting of methyl alcohol and ethyl alcohol, together with an esterification catalyst at a temperature between about 30 C. and about 50 C. for an esterification time of at least one-half hour and then rehardeningthe esterified thread by immersing said esterified thread in a bath containing formaldehyde and a metal salt of the threads in a 1% aqueous sodium carbonate solution is between about 40 and about 64.9% based on the weight of the oven-dried thread.

2. The process as claimed in claim 1 wherein the thread, after the initial hardening step and immediately before the esterification step, is pretreated with the alcohol used in the esterification step.

3. The process as claimed in claim 1 wherein the esterification catalyst used is sulphuric acid.

4. The process as claimed in claim 1 wherein the esterification is carried out at a temperature in the range of 35 to 50 centigrade.

5. The process as claimed in claim 1 wherein the proportion of alcohol present in the esterification bath is from 75 to 80 per cent.

6. The process as claimed in claim 1 wherein the initial hardening and the subsequent rehardening steps are carried out in a bath comprising iormaldehyde and sodium sulphate.

7. In a process for the production of artificial threads from proteins, by extruding a solution of a protein selected from the class consisting of milk casein, peanut protein, soya bean protein, and castor bean protein into a setting medium, hardening by immersing the freshly extruded thread so obtained in a bath containing formaldehyde and a metal salt chosen from the group consisting of sodium sulphate, magnesium sulphate, aluminum sulphate, and mixtures of said salts, until the thread is resistant to the solvent action of cold water, and stretching the thread during said hardening treatment, improving the wet properties of the thread by applying after the hardening step the steps of esterifying the thread at a temperature between about 30 C. and about 50 C. for an esterification time of at least one-half hour in a bath comprising an alcohol chosen from the group consisting of methyl alcohol and ethyl alcohol, together with an esterification catalyst and water, said water being in a proportion not exceeding 30% by weight based on the weight of the alcohol, and then rehardening the esterified thread by immersing said esterified thread in a bath containing formaldehyde and a metal salt chosen from the group consisting of sodium sulphate, magnesium sulphate, aluminum sulphate and mixtures of said salts, until the imbibition of the threads in a 1% aqueous sodium carbonate solution is between about 40 and about 64.9% based on the weight of the oven-dried thread.

8. The process as claimed in claim 7 wherein the proportion of water present in the esterification bath is from to percent.

9. The process as claimed in claim 7 wherein the thread, after the initial hardening step and immediately before the esterification step, is pretreated with a mixture of water and alcohol having the same composition as that present in the esterification bath.

10. In a process for the production of artificial threads from proteins, by extruding a solution of a protein selected from the class consisting of milk casein, peanut protein, soya bean protein, and castor bean protein into a setting medium, hardening by immersing the freshly extruded thread so obtained in a bath containing formaldehyde and a metal salt chosen from the group consisting of sodium sulphate, magnesium sulphate, aluminum sulphate, and mixtures of said sal until the thread is resistant to the solvent action of cold water, and stretching the thread during said hardening treatment, improving the wet properties of the thread by applying after the hardening step the steps of esterifying the thread in a bath comprising an alcohol chosen from the group consisting or" methyl alcohol and ethyl alcohol, together with an esterification catalyst and diet-hyl sulphate, at a temperature between about 30 C. and about 50 C. for a time of at least one-half hour, and then rehardening the esterified thread by immersing said esterified thread in a bath containing formaldehyde and a metal salt chosen from the group consisting of sodium sulphate, magnesium sulphate, aluminum sulphate and mixtures of said salts, until the imbibition of the threads in a 1% aqueous sodium carbonate solution is between about 40 and about 64.9% based on the Weight of the oven-dried thread.

11. The process as claimed in claim 10 wherein the diethyl sulphate is present in a proportion of about 30 percent by weight based on the weight of the alcohol.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,240,388 .Calva Apr. 29, 1941 2,475,879 Cline July 12, 1949 FOREIGN PATENTS Number Country Date 483,731 Great Britain Apr. 21, 1938 748,450 Germany Jan. 12, 1945 OTHER REFERENCES Evans et al., Textile Research Journal, April 1949, pages 202 to 211. 

1. IN A PROCESS FOR THE PRODUCTION OF ARTIFICIAL THREADS FROM PROTEINS BY EXTRUDING A SOLUTION OF A PROTEIN SELECTED FROM THE GROUP CONSISTING OF MILK CASEIN, PEANUT PROTEIN, SOYA BEAN PROTEIN AND CASTOR BEAN PROTEIN, INTO A SETTING MEDIUM, HARDENING BY IMMERSING THE FRESHLY-EXTRUDED THREAD SO OBTAINED IN A BATH CONTAINING FORMALDEHYDE AND A METAL SALT CHOSEN FROM THE GROUP CONSISTING OF SODIUM SULPHATE, MAGNESIUM SULPHATE, ALUMINUM SULPHATE AND MIXTURES OF SAID SALTS UNTIL THE THREADS IS RESISTANT TO THE SOLVENT ACTION OF COLD WATER AND STRETCHING THE THREAD DURING THE SAID HARDENING TREATMENT, IMPROVING THE WET PROPERTIES OF THE THREAD BY APPLYING AFTER THE HARDENING STEP THE STEPS OF ESTERIFYING THE THREAD IN A BATH COMPRISING AN ALCOHOL CHOSEN FROM THE GROUP CONSISTING OF METHYL ALCOHOL AND ETHYL ALCOHOL, TOGETHER WITH AN ESTERIFICATION CATALYST AT A TEMPERATURE BETWEEN ABOUT 30* C. AND ABOUT 50* C. FOR AN ESTERIFICATION TIME OF AT LEAST ONE-HALF HOUR AND THEN REHARDENING THE ESTERIFIED THREAD BY IMMERSING SAID ESTERIFIED THREAD IN A BATH CONTAINING FORMALDEHYDE AND A METAL SALT CHOSEN FROM THE GROUP CONSISTING OF SODIUM SULPHATE, MAGNESIUM SULPHATE, ALUMINUM SULPHATE AND MIXTURES OF SAID SALTS, UNTIL THE IMBITION OF THE THREADS IN A 1% AQUEOUS SODIUM CARBONATE SOLUTION IS BETWEEN ABOUT 40 AND ABOUT 64.9% BASED ON THE WEIGHT OF THE OVEN-DRIED THREAD. 